Method in the production of duplicate models



Jan. 11, 1955 SVEN VIKTOR LINDBOM 2,699,423

METHOD IN THE PRODUCTION OF DUPLICATE MODELS Filed April 27, 1951 INVENTORJ Sven Vi'ki'or lmc/kom United States Patent 'IVIETHODJN THE PRODUCTION -OF- DUPLICATE MODELS Sven. Viktor-Lindbom', Stockholm, Sweden, assignor, by

mesne assignments,- to:Husqvarna.-Vapenfabriks Aktiebolag, Huskvarna, Sweden This invention relates toa method in the production of duplicate -models of metal.

The model isprimarily intended to'be employed in the manufa'cturevof; pressing toolsin which preferably'irom powder is pressed onto-the duplicate model, and i the mouldso obtained is sintered.

The mainly=characterizingfeatures ofthe inventionreside in the steps :of covering an original model-.witha covermglayer-of a relatively easily fusible metal so that. a continuous shell is formed," after which the model is; removed from out of-'said' shell, covering the surface of said shell'remote from that of the cavityleft by said orig-- inalmodel with a protecting layer of electrically non-conducting material, precipitating electrically onto the surface of said shell remote'from that carrying said protectingrlayer a'continuousrlayer ofa metal having a higherfusing'point than' that of said covering'layer, and thereafter removing said coveringlayern The remaining material then constitutes an exact replica of the original model.

The invention-"will now 'be explained'more in detail, regergncc being-,had to theraccompanying. drawing in w 1c Fig.1 is'a planview-ofan original-model in:the-form of a comb made ofplastic material.

Fig. 2, to a'larger -scale-,-- shows a cross section: through the: teeth of 'the comb, taken on-=line--IIII in -Fig.'- 1, during 'a first stage of-the productionof the. duplicate model;v

Figs. 3 and 4show similarcross-sections duringga secnd landv third productionstage, respectively.

Fig. isa cross-section-throughaportion ofith1e: -resultingwduplicatemodel during theproduction ofa pressing tool by means of which articles according to Fig. 1 are intended to be manufactured.

Employing the embodiment illustrated in the drawing, the production of the duplicate model may be carried out in the following manner:

The original model 1 is placed on the upper ground surface of a sheet metal plate 2 bent in accordance with the model and is secured to said plate at spaced points by means of glue. The model 1 is thereafter sprayed all over with zinc by means of a metal spraying gun, for instance of the Schoop-Gun or Schoori-Gun type, until a layer having a thickness of about & to inch is obtained. The metal spraying is preferably carried out in periods, the metal being allowed to cool slowly after each spraying period. A fine grade structure of the zinc shell 3 will thereby be obtained. The whole assembly is thereafter removed from the base plate 2. In this operation, the original model 1 will, as a rule, accompany the zinc shell, but by exerting a slight force the model can be removed therefrom. However, if difiiculty should be encountered in removing the original model from the zinc shell, then the model could be dissolved by means of any suitable liquid, it being, of course, of importance to use a solvent which does not attack the zinc. The zinc shell 3 (Fig. 3) being an exact matrix of the original model, is now covered on its outer surface with an electrically nonconducting protecting layer 4 of, for instance, lacquer. Onto its opposite surface is then electroplated a layer 5 of Copper. The electro-plating operation is preferably interrupted when the copper layer has obtained a thickness of about 0.08 to inch. The protecting layer is now removed, and the zinc layer is removed by etching with an acid, such as hydrochloric acid. The remainder forms a 2,699,423 Patented J an. v1 1, 1955.

ice

2. perfect copper replica of the original model 1. The cavities on the back of the duplicate model 6 (Fig. 5) are preferably'filled in with tin 7 whereby the rigidity of the model is increased.

A pressing tool isproduced from the duplicate modelin awell-known manner. Referring to Fig. 5, the duplicate-model 6 is placed in a press mould 8 the bottom of which has the same curvature as the duplicate model. Iron powder 10'is introduced in the mould and pressed to'suitable compactness. The pressed body is thereafter inserted .in a furnace 'to-become-sintered. The pressing tool. thus obtained may, if desired, be reinforced by well-known means..

Several modifications of the method describedof-producing the duplicate model are possible without departing from the scope of the invention. Instead of spraying the plastic model withmetal, it may be covered with electrically conducting. material in any suitable other manner. Forexample, the original model may be introduced in a vacuum chamber in which a metal is vaporized by electrical means, so'that the metal-vapor precipitates onto thernodel and forms a thin metal layer. thereon. In similar manner an electrically conducting layer may be applied onto the model by cathode atomization carried out by high tension electrical current, or the model may be chemically metallized, for example, silverplated.

After having provided the-model with such a thin, electrically conducting metal layer, the Whole assembly is immersed. in an-electro-plating bath whereby a thicker metal layer is obtained on the model. Thereafter, the-latter maybe removed from out ofthe metal shell obtained; after which the latter is provided on its'outer surface with a lacquerlayer and is then-again immersed in an electroplating bath in which the same isprovided with a metalcovering on'the wall ofthe cavity left by the original model:

Other-metalsthan zinc and'copper might, of course, come into consideration. Thus, tin could, with advantage, be sprayed 'onto the original model and be fused away in thelater stage of the production. Tin could also be applied by electro-plating;

If the original. model consists of an easily fusible metal, the-layer 3 could be applied by electro-plating, in which case thefusing point of the plating metal'must be higherthan: that of the original model. The original model is thereafterfusedxaway leaving-a metal matrix. The latter is thereafter-provided in: the: cavity left by the original modelwith an electro-platedlayer of another metal which should have a fusing point which is higher than that of the metal matrix. The latter is then removed, for instance, by fusing, upon which the assembly is heated up to a temperature which is slightly higher than the fusing point of the metal matrix 3. The metal matrix 3 might instead be removed by etching with an acid.

The invention also includes duplicate models produced according to any of the methods disclosed in the foregolng.

What I claim and desire to secure by Letters Patent is:

1. An improved method of manufacturing pressing tools comprising applying a covering layer to one side surface of a model of the article the configuration of which is to form the face of the tool so that a continuous shell is formed on said side surface, removing the model from the shell, electrically precipitating a continuous layer of relatively hard metal on the impression surface of said shell to form a duplicate of the model, removing said shell, applying a metallic backing to the surface of the duplicate opposite to that from which the shell had been removed, compressing and compacting iron powder against said duplicate on the side opposite to said backing and sintering said compacted iron powder to a body having an impression of the said one side surface of the model to produce a pressing tool of sintered iron powder having a positive duplicate of the model on its pressing face.

2. An improved method of manufacturing pressing tools comprising applying a covering layer of a relatively easily fusible metal to one side surface of a model of the article the configuration of which is to form the face of the tool so that a continuous shell is formed on said side 'sur face, removing the model from the shell, covering the surface of the shell opposite to that which had been applied against the model with a layer of electrically nonconducting material, electroplating the surface of the shell opposite to that covered with said non-conducting material with a continuous layer of a relatively hard metal having a fusion point higher than that of 'said shell to form a duplicate of said model, removing said shell by fusing and applying a metallic backing against the surface of the duplicate opposite to that from which the shell had been removed, compressing metal powder into a compact about said duplicate and against the face thereof opposite to that to which the backing had been applied and finally sintering said compact.

3. An improved method of manufacturing pressing tools comprising spraying a covering layer of a relatively easily fusible metal on to one side surface of a model of the article the configuration of which is to form the face of the tool so that a continuous shell is formed on said side surface, removing the model from the shell, electrodepositing a continuous layer of iron on the impression surface of said shell to form a duplicate of the model, removing said shell, applying a metallic backing to the surface of the duplicate opposite to that from which the shell had been removed, compressing and compacting iron powder against said duplicate on the side opposite to said backing and sintering said compacted iron powder to a body having an impression of the said one side surface of the model.

, 4. An improved method of manufacturing pressing tools comprising supplying plural layers of a relatively easily fusible metal to one side surface of a mold of the article the configuration of which is to form the face of the tool so that a continuous shell is formed on said side surface while permitting the metal to slowly cool after each layer is applied, removing the model from the shell, electroplating the surface of said shell that had been applied against the model with a continuous layer of relatively hard metal to form a duplicate of said model, removing said shell, applying a metallic backing to the surface of the duplicate opposite to that from which the shell had been removed, compressing iron powder into a compact by means of said duplicate and finally sintering said compact.

5. An improved method in the manufacture of pressing tools comprising electroplating one side surface of a model of relatively easily fusible metal of the article the configuration of which is conformed to the impression surface of the tool with a metal having a higher fusing point than that of the model so that a continuous shell is formed on said one side surface, removing said model from the shell by fusing, electrically precipitating a continuous layer of relatively hard metal on to the surface of the shell from which the model has been removed to form a duplicate of the model, removing the shell and applying a metallic backing to the surface of the duplicate opposite to that from which the shell had been removed, compressing and compacting iron powder against said duplicate on the side opposite to said backing and sintering said compacted iron powder to a body having an impression of the said one side surface of the model.

6. In tool manufacture, a method comprising supporting a model having the configuration to be imparted to the tool upon a metal plate bent in accordance with the general configuration of the model, securing the model against said plate, spraying zinc upon the exposed surfaces of the model until a layer having the thickness of between A; to A2 inch is obtained, removing the model with the zinc shell thereon from the plate, removing the model from the shell, applying a layer of electrically non-conducting material to the surface of the shell opposite to that which had been applied against the model, electroplating copper on the opposite surface of the shell to form a continuous layer having a thickness of between 0.08 to 0.10 inch, removing the layer of non-conducting material, removing the zinc shell so that the copper layer constitutes a duplicate of the original model, applying a backing of tin to the face of said duplicate opposite to that from which the non-conducting layer has been removed to enhance the rigidity of the duplicate, confining the duplicate in a mold the bottom of which has a curvature corresponding to that of the duplicate with the backing resting against the bottom, compressing and compacting iron jowder into the mold about the duplicate, and finally sintering the compacted iron powder body to form a pressing tool having an impression surface conforming in configuration to that of the original model.

7. In tool manufacture, a method as defined in and by claim 6 in which the zinc is sprayed in plural layers and each successive layer is permitted to slowly cool before a subsequent layer is applied.

References Cited in the file of this patent UNITED STATES PATENTS 783,176 Cheney Feb. 21, 1905 1,513,120 Madsen Oct. 28, 1924 1,703,177 Short Feb. 26, 1929 2,182,775 Abouchor Dec. 12, 1939 2,198,253 Koehring Apr. 23, 1940 2,280,865 Stossel Apr. 28, 1942 2,327,762 Bull Aug. 24, 1943 2,349,920 Welcome May 30, 1944 2,363,337 Kelley Nov. 21, 1944 2,540,212 Paget Feb. 6, 1951 

1. AN IMPROVED METHOD OF MANUFACTURING PRESSING TOOLS COMPRISING APPLYING A COVERING LAYER TO ONE SIDE SURFACE OF A MODEL OF THE ARTICLE THE CONFIGURATION OF WHICH IS TO FORM THE FACE OF THE TOOL SO THAT A CONTINUOUS SHELL IS FORMED ON SAID SIDE SURFACE, REMOVING THE MODEL FROM THE SHELL, ELECTRICALLY PRECIPITATING A CONTINUOUS LAYER OF RELATIVELY HARD METAL ON THE IMPRESSION SURFACE OF SAID SHELL TO FORM A DUPLICATE OF THE MODEL, REMOVING SAID SHELL, APPLYING A METALLIC BACKING TO THE SURFACE OF THE DUPLICATE OPPOSITE TO THAT FROM WHICH THE SHELL HAD BEEN REMOVED, COMPRESSING AND COMPACTING IRON POWDER AGAINST SAID DUPLICATE ON THE SIDE OPPOSITE TO SAID BACKING AND SINTERING SAID COMPACTED IRON POWDER TO A BODY HAVING AN IMPRESSION OF THE SAID ONE SIDE SURFACE OF THE MODEL TO PRODUCE A PRESSING TOOL OF SINTERED IRON POWDER HAVING A POSITIVE DUPLICATE OF THE MODEL ON ITS PRESSING FACE. 